This invention relates to semiconductor injection lasers and, more particularly, to heterojunction injection lasers adapted for longitudinal mode and fundamental transverse mode operation.
Higher power outputs are being sought in semiconductor junction lasers to meet requirements necessary for optical fiber transmission, optical disc writing and integrated optical components and circuits. To this end, control of single longitudinal mode selectivity and fundamental transverse mode operation have become of increasing interest. For example, development of longitudinal mode selectivity is important in order to provide high bit rate optical fiber communication. Also fundamental transverse mode confinement and control would optimize the standing wave for greater power output useful in optical disc applications.
Also there is need in integrated optical-circuitry to provide efficient light couplers from one waveguiding cavity to another independent waveguiding cavity. The need arises from the fact that in fabricating optical communication chips, light from an outside laser must be efficiently transferred to a waveguide and then transferred out to another light coupled component, such as, another light transmitting cavity or fiber optic transmission line.
In longitudinal mode selectivity, coupled laser cavities of different cavity lengths would provide a multicavity structure so that the combined effect of reflecting light in the two light transmitting cavities would be to enhance the single longitudinal mode operation and provide a higher power output. Such a structure is disclosed in an article entitled "The Bent-Guide Structure Al GaAs-GaAs Semiconductor Laser" by Nobuo Matsumoto in IEEE Journal of Quantum Electronics, Vol. GE-13, No. 8, pages 560-564, August 1977. However, the L-type laser disclosed requires sophisticated fabricating technique including the provision of a smooth and polished finish on the internal bent-guide surface from which the two light guiding cavities of different lengths are defined.